There have been many advances in solid state materials useful in conductive and chemoresistive devices and in sensory devices for determining the presence a variety of analytes. Tailoring the properties of these materials to effect a specific function or optimize performance is complex because properties can be dependant upon the overall architecture of the material, which often is unpredictable.
One class of solid state materials is conducting polymers. These polymers typically include organic structures possessing a degree of unsaturation to allow electronic communication throughout a polymeric structure. Because polymers in general are synthesized from monomer components, the design of the conducting properties of a conducting polymer can be facilitated by engineering the monomer component to a desired specificity. Moreover, polymers containing both organic and metal ion components afford a larger number of variables over organic-based polymers through the incorporation of a diverse number of metal ions. A variety of synthetic strategies are described in numerous prior art references.
Zotti et al. disclosed in situ conductivity of some polypyrroles and polythiophenes redox modified with pendant ferrocene groups. It was found that the electron hopping rate through the conductive polymer backbone is increased by a decrease of the ferrocene backbone distance and by conjugation of ferrocene with the backbone itself. Chem. Mater. 1995, 7, 2309.
Cameron et al. describes a benzimidazole-based conjugated polymer with coordinated [Ru(bpy).sub.2 ].sup.2+, moieties, providing direct electronic communication between the ruthenium complex and the polymer. Chem. Commun. 1997 303.
Audebert et al. reports a series of conducting polymers based on metal salen containing units based on mononuclear copper.sup.II, cobalt.sup.II, nickel.sup.II and zinc.sup.II complexes. Under carefully chosen conditions, thick electroactive polymer deposits are formed upon electrochemical oxidation of the monomer in solution. New. J. Chem. 1992, 16, 697.
Segawa et al. describes a series of highly ordered conducting polymers through the construction of sequentially ordered one- or two-dimensional metalloporphyrin polymers connected by oligothiophene bridges. The one-dimensional phosphorus(V)porphyrin polymers were linked toward the axial direction of the porphyrin ring whereas the two-dimensional metalloporphyrin polymers were linked equatorially by oligothienyl groups. Both polymer types were prepared by electrochemical polymerization techniques.
U.S. Pat. No. 5,549,851 discusses silicon containing polymers admixed with an amine compound. A highly conductive polymer composition is formed upon doping with an oxidizing dopant, typically iodine and ferric chloride. The composition has improved shapability and is easily applicable to form a highly conductive film or coating.
U.S. Pat. No. 4,839,112 discloses methods of fabricating low dimensionally electroconductive articles comprised of cofacially stacking organomacrocycles, preferably cofacially stacking phthalocyanines. The cofacially stacked composition in strong Bronsted acid is formed into a desired shape such as a fiber or film.
The integration of receptors into conducting polymer frameworks has been shown to produce materials which provide changes in physical characteristics upon binding of targeted analytes. Devynck et al. describes a material containing CO(III) porphyrin sites. Variations in the Co(III)/Co(II) redox couple are observed upon exposure to pyridine and with changing pyridine concentrations.
U.S. Pat. No. 5,250,439 reports the use of conductive sensors to determine the presence or concentration of a predetermined analyte in a test sample by measuring the change in conductivity of a layer of an organic conducting polymer. This conductivity change results from generating a dopant compound that migrates to the detection zone of the conductive sensor to dope the layer of conducting polymer. One example describes the dopant compound as comprising molecular iodine, formed in a reaction between iodide ions, a peroxidase enzyme or a molybdenum(VI) catalyst in the reaction zone of the device to determine the presence or concentration of glucose.
U.S. Pat. No. 4,992,244 discloses a chemical microsensor fabricated by using Langmuir-Blodgett techniques. The chemical microsensor is a film based on dithiolene transition metal complexes which display differing degrees of current changes upon exposure to a particular gas or vapor and its concentration.
Despite numerous advances in polymeric materials as chemoresistive and sensory devices, there remains a need to improve the conductivity level of these materials. Moreover, improvements in fabricating films of these materials, such that conductivity properties remain optimal at a desired film thickness, would be desirable. There also remains a need to produce sensory materials for a wider variety of analytes. Transition metals offer unique and desirable characteristics for the creation of sensory materials that are sensitive to anions as well as small molecules. In spite of this and other potential applications, few studies have been directed at the development of transition metal/conducting polymer hybrid systems.